Monday, 30 December 2013

RACE to Goals Model – The Defence

Prior to the season starting, I introduced the RACE to Goals Model, which you can find here, and I suggest you have a read of that before you continue with this one if you want to have a full description of the different metrics and how they are calculated.

Essentially, I am looking at the same metrics, but this time flipped to a defensive point of view, so the rate of shots conceded, the Defensive Efficiency, and the conversion of chances conceded by each type.

I will describe Defensive Efficiency here though, as it’s calculated slightly differently. Whereas Creative Efficiency attempts to show how good a team is at creating good chances, measured as the proportion of Clear Cut Chances to Total Shots, Defensive Efficiency attempts to show how good a team is limiting the amount of good chances the opposition has, and is measured as the proportion of Normal Chances conceded to Total Shots conceded (%NC). So the higher the number, the lower the percentage of Clear Cut Chances conceded, and the more efficient the defence is.

The benchmark numbers are essentially the same, the slight difference being own goals, and those ‘shots’ by players on the defending team that lead to own goals are also included.

The table below shows how well the teams performed last season against the 4 metrics.

The team that conceded the fewest shots was Tottenham, with only 370 over the entire season, so a touch under 10 shots a game. At the other end of the scale were Reading, who conceded 706 shots, the worst by over 60 shots.

Like with the original article, I feel the raw numbers in the table are a little hard to read, so again I’ll add context and measure each metric as the percentage difference from the benchmark team. From the a defensive point of view, having shots and conversion rates below the benchmark is good, but this is not the case for Defensive Efficiency, so I’ve highlighted this in the table as anything in red as being ‘bad’.

As with Creative Efficiency, Manchester United also had the best Defensive Efficiency, limiting their opponents to only 8.2% of their shots coming from CCCs, with Manchester City being the only other team to have a Defensive Efficiency of over 90%, seeing them perform 6% and 4% better than average respectively. The team with the worst Defensive Efficiency was Newcastle, who allowed over 18.5% of all chances against to be CCCs; however the 2nd worst team, perhaps surprisingly considering how few shots they conceded, was Tottenham, allowing almost 18%, and possibly showing the risk of playing with a high defensive line.

Looking at the conversion rates it becomes clear why Wigan struggled last season. They had by the worst rate of CCCs conceded, in fact at 52.7%, they are the only team over the 3 years of data that conceded more than half the CCCs that they faced. They were also the 2nd worst at stopping Normal Chances being conceded. Reading actually had the best rate when it came to stopping CCCs in the league, but unfortunately for them, when you allow the opposition to create over 100 CCCs in total, you will still concede a lot of goals.

No teams outperformed or underperformed all 4 of the metrics compared to the benchmark. Only 4 teams, the two Manchester clubs, Chelsea and Swansea outperformed on 3 of the benchmarks. Liverpool join Utd, City and Chelsea as the only teams who conceded fewer shots than the benchmark whilst also having a higher than average Defensive Efficiency. Despite conceding the fewest shots, we can see why 7 teams conceded less goals than Tottenham following their underperformance in the 3 other metrics.

Converting the metrics into Expected Goals, we see how badly Wigan performed. Whilst they would have been expected to concede just less than 54 goals from the shots that the opposition had, which was only the 10th lowest, they actually conceded 73 (+19.1 goals more than expected). The other big underperformers were Southampton (+9.7 goals), Newcastle (+9.0 goals) and Aston Villa (+7.9 goals). The biggest overperformers were Everton (-9.5 goals), Sunderland (-8.7 goals), Stoke (-6.4 goals) and Arsenal (-6.0 goals).

In my next posts I will combine some of the attacking and defending metrics together to analyse team’s performances in some new ways, and see how the teams have performed so far this season.

About Me

Another blog mainly about football stats, and another blog mainly about Liverpool. But have you seen one with football finance and fantasy football as well? Yes, you probably have.
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